1. Technical Field
The present disclosure relates to automatic pumps for tires and more specifically to pumps that use changes in orientation due to tire rotation and gravitational force to drive pumps to automatically inflate tires.
2. Introduction
Tires are a critical part of modern transportation. However, proper tire inflation is an important factor in the safety, efficiency and cost of using tires. Neither underinflation nor overinflation is an optimal condition for tire longevity or safety. Overinflation can lead to unsafe wear patterns, lower traction and increased potential for a catastrophic failure or blowout of the tire during otherwise normal operation. Underinflation lowers the fuel efficiency of tires, increases wear, lowers the tire sidewall (lateral) stiffness making the tire less safe and increases the potential for catastrophic failure or blowout of the tire during otherwise normal operation. All rubber-based, modern tires lose some amount of gas due to the natural porosity of rubber. These porosity losses can be minimized by using larger air molecules (Nitrogen) than air. However, the porosity losses are only reduced, not eliminated.
Temperature can also affect tire inflation. Under higher temperatures, the tire pressure increases, while under lower temperatures, the tire pressure decreases. One solution is for users to manually check tire inflation periodically, but this is a difficult task, requires training and significant user time. Further, some portion of the user population will never check their tire inflation due to inconvenience, regardless of the benefits that proper inflation provide. Tire inflation is a problem that many drivers do not care enough about to invest the time to check or correct until the problem is so bad that the tire, and consequently the vehicle, become undrivable, or unsafe. An automatic approach to tire inflation that does not require end-users, i.e. the drivers of these vehicles, to spend time and effort would be significantly preferable.